Mitt Romney on Wednesday renewed his warnings about Russia being a dominant world threat, hours after Moscow began airstrikes in Syria and urged the U.S. to stay clear.

“You don't let the Russians tell us that we can't fly over Syria,” Romney said during the Aspen Institute’s Washington Ideas Forum in the nation's capital.

As the 2012 Republican presidential nominee, Romney was mocked by Democrats for saying that Russia was the country’s top geopolitical foe.

However, Russian President Vladimir Putin has since flexed his country’s military might in Ukraine and Syria, where Moscow is providing military support to the regime of President Bashar al Assad in the years-long civil war.

In Ukraine, Russia is helping rebels trying to topple a new, pro-Democratic government backed by the United States and western allies.

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The Obama administration stressed Wednesday that it would not leave Syrian airspace during Russian missions.

Still, Romney urged the administration to put more effort into defeating the Islamic State, which now controls large swatches of Syria.

He argued that the rise of the Islamic State is the result of two administration failures. The first was failing to give stronger support to the rebel forces against Assad, as Hillary Clinton suggested when secretary of state.

“We did not do that,” Romney said during a roughly 15-minute interview at the event Wednesday.

And the second, he said, was not securing an agreement to keep U.S. soldiers in Iraq, where the Islamic State, or ISIS, has also flourished.

“The result of those two bad decisions is we now have ISIS,” Romney said. “Though the president said Assad must go, the combination of these events has made it very difficult for him to accomplish his mutual objectives of getting rid of Assad and eliminating ISIS.”

Romney suggested Obama’s overall foreign policy is a “disaster” and that the president has created many of his own problems by eliminating options or by waiting too long or by “painting himself into a corner.”

He and other Republicans repeatedly argue that Obama said Assad would “cross a red line” by using chemical weapons on civilians but failed to take action amid compelling, independent evidence of such attacks.

Romney also argued, as he did in 2012, that the administration has turned its back on Israel, the United States’ oldest and strongest Middle East ally.

“The president has been a foreign policy disaster,” Romney said. “You may love the president for a lot of reasons. His rhetoric might be soaring, but the results have been terribly disappointing.”